OE3ZK wrote:
>What I read in these responses is that many
of us see filtering /bandwidth reduction as
the sole means of improving the ability to
recover information from noise.
Gert, I believe I said filtering / BW
reduction is the way **Orion's NR** works.
There are other methods, but they involve
much more CPU processing power than Orion has
available and considerably more latency (i.e.
several seconds delay) as the signal is
processed by the CPU. The ultimate narrow
bandwidth method is QRSS which uses a 0.033 Hz
filter BW and takes literally hours to complete
a 2-way contact but that's not very practical.
>What I fail to understand is the claim by users
of Linrad and Winrad that DSP noise reduction is
improved by processing noise in a much wider band
than the signal itself. It appears to be born out
by examples, I just don't know why...
You might want to join the Winrad
discussion group or directly ask SM5BSZ, I2PHD
or WA6KBL your question.
http://winrad.org/mailman/listinfo/winrad_winrad.org
Also see the following websites:
http://www.weaksignals.com/
http://www.nitehawk.com/sm5bsz/index.htm
Your question is an interesting one
because this is how my ear/brain works also. I
also hear weak signals better at wider bandwidths,
**IF** the noise is Gaussian. I prefer a filter
much wider (typically 300-600 Hz) than the narrowest
available (50-100 Hz). Somewhere on SM5BSZ's site
he comments that there are two schools of thought
about copying weak signals. Some of us prefer very
narrow filters and some of us prefer wider filters.
Unfortunately Leif's site is very large and I cannot
find that link at the moment.
Let us know if you get the answer to your
question.
73, Bill W4ZV
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